The origin of the measles virus, currently capturing headlines across the country with 121 cases in the US (and 147 in the region of the Americas) so far this year, is likely zoonotic. Like almost every infectious disease of humans, animals likely played a part and the virus jumped into humans. The virus that measles evolved--I wanted to use that word on Darwin Day--from is canine distemper.

Canine distemper virus is a member of the same viral family as measles (paramyxovirus) and was first described in the early 20th century. The symptoms it causes include fever, nasal discharge, and eye inflammation (sound familiar?). Vomiting and diarrhea, lethargy and loss of appetite, labored breathing and/or coughing, and hardening of footpads and nose, and other symptoms can also occur. It is vaccine preventable and remains a leading cause of infectious disease death in dogs.

There is good reason to believe that canine distemper virus (or the related and now eradicated rinderpest virus of cattle) jumped into humans and evolved into measles when human populations reached the threshold population density needed to sustain human-to-human transmission of the virus. Indeed measles vaccination protects canines against distemper.

It's puzzling to me that we don't hear about an anti-vaccine movement amongst dog owners yet amongst parents of human children we have no such luck.